The present invention relates to a multipurpose projector, more particularly to a multipurpose projector with a detachable projecting unit adapted to be detachable from a zoom lens and an image sensor in an optical system for carrying out multipurpose functions of an overhead projector (OHP) which projects a still image onto a screen, an LCD projector which projects moving pictures onto the screen, and a print copier and image copier, according to selection on a menu.
Conventional OHPs which project a still image onto a screen, include a pass-through type OHP as shown in FIG. 1 and a reflection type OHP as shown in FIG. 2. The projecting process of each will be explained in detail.
Upon turning on the projector after placing a transparent film of a still image on a Fresnel lens 22 in top of a body 21 of the projector, light from a light source is reflected at a reflection mirror to the Fresnel lens 22, and focused by the Fresnel lens 22 onto a projecting unit 23. Then, the still image is projected to a projecting mirror 24 with the image diverged, and therefrom reflected onto a screen (not shown) in front of the projecting mirror 24.
This projecting process explained herein is the same for the pass-through type OHP and the reflection type OHP, except that the pass-through type OHP has its light source and the reflection mirror inside of the body 21 while the reflection type OHP has them inside of the projecting unit 23.
Such OHPs can only project a still image onto a screen, with inconvenience of continuous replacement of the transparent films of still images.
A process of projecting moving pictures onto the screen, of a conventional LCD (Liquid Crystal Display) projector that projects moving pictures onto the screen having a system as shown in FIGS. 3 and 4, will be explained in detail.
The optical system of the LCD projector shown in FIG. 4 is disclosed in the Korean Patent application No. 94-23428 with a title "Combined slide and picture projector", applied for by the same applicant.
Upon turning on the LCD projector after connecting the projector to a VCR (Video Cassette Recorder) or a PC (Personal Computer), a signal separated into three color signals of red, green and blue coming from the VCR or the PC individually enters into a relevant liquid crystal panel of a first, second, and third liquid crystal panels 32, 33 and 34 disposed in the body 31 and on the same time a light source 35 generates three colored(red, green, and blue) lights. The three colored light, absorbed of its heat as it is filtered through a filter 36, is incident to a first reflection mirror 37 which is adapted to reflect red light only, and reflected at a right angle with the path of the red light. The remaining green and blue lights pass through the first reflection mirror 37 unchanged and then are incident to a second reflection mirror 38 which is adapted to reflect green light only. The green light is reflected at a right angle with the path of the green light, while the blue light passes through the mirror 38 as it was.
In the meantime, the red light reflected at the first reflection mirror 37 is reflected again at a right angle at a third reflection mirror 39, to pass through the first liquid crystal panel 22. At this time, a red image from the first liquid crystal panel 32 is carried by the red light passing through the panel 32 and is then incident to a fourth reflection mirror 40 which is adapted to reflect red color at a right angle.
And, the blue light passed through the second reflection mirror 38 is incident to a fifth reflection mirror 41 and a sixth reflection mirror 42 in series, which change its path at right angles, and passes the third liquid crystal panel 34. At this time, a blue image from the third liquid crystal panel 34 is carried by the blue light passing through the panel 34, then incident to a seventh reflection mirror 43 which is adapted to reflect blue color at a right angle.
And, the green light reflected at the second reflection mirror 38 passes through the second liquid crystal panel 33. At this time, a green image from the second liquid crystal panel 33 is carried by the green light passing through the panel 33 and is then incident to the fourth reflection mirror 40 which only reflects red color and the seventh reflection mirror 43 which only reflects blue color to pass them unchanged.
Then, the red image having its path changed at a right angle on incidence to the fourth reflection mirror 40, the blue image having its path changed at a right angle on incidence to the seventh reflection mirror 43, and the green image having been incident to the fourth reflection mirror 40 which only reflects red color and the seventh reflection mirror 43 which only reflects blue color to pass them unchanged, are combined as they pass through a projecting lens 44 in the front side of the body 31 and projected onto a screen (not shown).
Though such a conventional LCD projector has a capability of projecting moving pictures, it has a problem in that it can not be used in overhead projection and also for other purposes, such as print copying and image copying, at all. Moreover, unlike with an OHP, the conventional LCD projector has a problem in that an image from the projector can not be selected for pointing a part on the image.
In conclusion, since aforementioned OHP and LCD projector can only be used for their inherent functions, consumers must purchase projectors having a desired function individually as the case demands.